Gap reduction through use of detectors

ABSTRACT

There is disclosed an apparatus and method for controlling a traffic signal means for alternately allocating &#39;&#39;&#39;&#39;go&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;stop&#39;&#39;&#39;&#39; signals to at least a first and second conflicting traffic lane wherein the first traffic lane has vehicle detection means associated therewith for detecting vehicles in the first phase, the second traffic lane has at least a first and second detection means associated therewith for detecting vehicles in the second traffic lane, a first circuit means coupled to the vehicle detection means for developing a signal upon detection of a vehicle by the vehicle detection means; and, timing circuit means coupled to the first circuit means for deactivating the first detection means of the second traffic lane at a predetermined period of time after a signal is developed by the first circuit means in response to the detection of a vehicle by the vehicle detection means.

United States Patent [72] Inventors Fr nk W- Hill Primary Examiner-William C. Cooper Moline; Attorney-Meyer, Tilberry and Body William W. Huppert, Moline; James J. Vandemore, Geneseo, all of III. [2]] Appl. No. 834,758 [22] Filed June 19, 1969 [45] Patented Oct. 12, 1971 [73] Assignee Gulf 8: Western lndustnes New ABSTRACT: There is disclosed an apparatus and method for controlling a traffic signal means for alternately allocating go and stop signals to at least a first and second conflicting [54] GAP REDUCTION THROUGH USE OF traffic lane wherein the first traffic lane has vehicle detection DETECTORS d h d m 22 Claims 7 Drawing Figs. means associate t erewlt or etectmg ve 1c es in e irst phase, the second traffic lane has at least a first and second de- U-S. tection means associated therewith for detecting vehicles in 31 A the second traffic lane, a first circuit means coupled to the [51] Int. Cl G08g l/08 hi l detection ea for developing a signal upon d t [50] Field of Search 340/3I A, i f a vehicle by the vehide detection mcans; and timing 37 circuit means coupled to the first circuit means for deactivating the first detection means of the second traffic lane at a [56] References cued predetermined period of time after a signal is developed by the FOREIGN PATENTS first circuit means in response to the detection of a vehicle by 1,076,926 7/1967 Great Britain 340/37 the vehicle detection means,

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' SHEET 2 BF 5 (be DETECTOR TO LC I ALL (DA DETECTORS I TO Lc LS-l jDA I 3 f 5 F v /G| {LD'I F I L-I/ FIG. 2

L-A V mvsmons. FRANK w. HILL WILLIAM w. HubPERT 8 BY JAMES J. VANDEMORE Maya, 71154244; 8 Body ATTORNEYS PATENTED 2 3.613 O74 SHEET 5 BF 5 TIME "0 I 2 GAP A DISTANCE HI H 2 H2 FIG-5A H 3 3 H4 u f 1 F'IME GAP A\ H DISTANCE H2 H H3 3 FIG. 5B

H4 U 1 1 1 TIME INVENTORS.

FRANK w. ,HlLL WILLIAM;.W. HUbPERT a BYJAMES J. VANDEMORE ATTORNEYS CAP REDUCTION THROUGH USE OF DETECTORS This application pertains to the art of traflic control and, more particularly, to improved gap reduction circuitry to be employed with a traffic controller.

The invention is particularly applicable to a two or more phase, full-actuated traffic controller and will be described with particular reference thereto; although, it is to be appreciated that the invention may be used in conjunction with various types of traffic controllers including, for example, a two-phase, semiactuated trafiic controller.

Traffic controllers having time-waiting, gap reduction circuits are known in the art of traffic control. One purpose of such a circuit is to effect a change in right-of-way signals allocated to two intersecting traffic lanes as a function of the elapsed time a vehicle is waiting (known as time-waiting period") in the lane which is denied right-of-way movement, as well as the actual time gap between successive vehicles in the phase to which right-of-way is allocated. Generally, when the actual time gap exceeds a predetermined or referenced time gap, and/or after a predetermined time-waiting period has elapsed, a change in allocation of right-of-way is initiated. Provisions may be made for last car passage time to permit the last vehicle in the phase having righbof-way to reach the intersection before that phase is denied right-of-way movement.

. Various aspects of such time-waiting, gap reduction circuits are disclosed in U.S. Pat. application, Ser. No. 586,127, entitled Traffic Controller Having Improved Time Waiting'Gap Reduction Circuit, filed Oct. 12, 1966, now U.S. Pat. No. 3,466,599, and assigned to the same assignee as the present invention. That patent application is directed toward a timewaiting, gap reduction circuit which includes a passage time having means for developing a first signal which progressively varies in a linear manner with elapsed time between successive vehicle detections, and a time-waiting timer having means for developing a second signal which progressively varies in a linear manner with elapsed time during the period that a vehicle is waiting in the lane to which a stop" signal is displayed, and means for comparing the first and second signals and developing a go terminating signal when the first and second signals attain a predetermined relationship with respect to each other.

The present invention is directed toward circuitry for providing gap reduction measurements which may be utilized with relatively noncomplex, conventional intersection controllers. In addition, the gap reduction circuitry may be utilized with such a conventional controller without necessitating changes to the internal circuitry of the controller, thereby providing gap reduction circuitry which is compatible with existing traffic controllers.

The present invention contemplates new and improved gap reduction circuitry which overcomes all of the above-referredto problems, and others, and provides circuitry which is simple in construction and installation.

The present invention contemplates gap reduction circuitry to be utilized with a trafiic controller for controlling allocation of go and stop signals to at least two intersecting traffic lanes wherein the first traffic lane includes vehicle detection means associated therewith for detecting vehicles in the first lane, and the second traffic lane includes at least a first and second detection means associated therewith for detecting vehicles in the second traffic lane. A first circuit means is coupled to the vehicle detection means of the first traffic lane for developing a signal upon actuation of the vehicle detection means, and a timing circuit means is coupled to the first detection means for deactivating the first detection means of the second traffic lane at a predetermined period of time after a signal is developed by the first circuit means upon actuation of the vehicle detection means of the first traffic lane.

In accordance with a more limited aspect of the present invention, the gap reduction circuitry includes circuit means couples to the second detection means for deactivating the second detection means at a second predetermined period of time after a signal is provided by the first circuit means upon actuation of the vehicle detection means of the first traffic lane.

Still further in accordance with the invention, there is provided a method of alternately allocating go" and "stop" signals to at least a first and second lane by utilizing vehicle detection means associated with the first traffic lane first and second detection means associated with the second traffic lane, first circuit means coupled to the vehicle detection means. In accordance with the method, the steps include: activating the traffic signal means to display a stop signal to one of the traffic lanes and a go signal to the other one of the traffic lanes; activating the first, second and vehicle detection means; detecting trafiic in one of the traffic lanes with the vehicle detection means; developing a signal with the first circuit means in response to a detection of traffic by the vehicle detection means; detecting traffic in the other of the traffic lanes with the first and second detection means; developing a control signal with the first and second detection means in response to the detection of a vehicle by the first and second detection means, respectively; applying said control signals developed by the first and the second detection means to a traffic signal means to thereby allocate the go and stop signals to the traffic lanes; deactivating the first detection means at a predetermined period of time after a signal is developed by the first circuit means so that at a predetermined period of time after a signal is developed by the first circuit means the first detection means becomes inefiective in controlling the operation of a traffic signal means in allocating go and stop signals to the traffic lanes.

The primary object of the present invention is to provide an improved 'gap reduction circuit, wherein gap reduction is obtained by deactivating at least one of a plurality of trafiic detection means associated with a first traffic lane at a predetermined period of time after a vehicle is detected in a second traffic lane.

Another object of the present invention is to provide a gap reduction circuit which may be utilized with conventional traffic controllers.

Another object of the present invention is to provide a gap reduction circuit which may be utilized with conventional traffic controllers without necessitating changes in the internal circuitry of the trafiic controller.

A still further object of the present invention is to provide an improved gap reduction circuit which may be added to existing conventional traffic controllers as the traffic demands upon the controller change.

Another object of the present invention is to provide an improved gap reduction circuit wherein linear gap reduction measurements may be obtained.

In accordance with a still further object of the present invention, there is provided a gap reduction circuit wherein exponential gap reduction measurements may be obtained.

Another object of the present invention is to provide a gap reduction circuit in which the vehicle detection means may be positioned with respect to each other to provide any desired gap reduction measurements.

These and other objects and advantages of the invention will become apparent from the following description of the preferred embodiment of the invention as read in connection with the accompanying drawings in which:

FIG. I is a block diagram of a traffic controller incorporating the preferred embodiment of the present invention;

FIG. 2 is a schematic circuit, block diagram of the preferred embodiment of the invention as illustrated in FIG. 1;

FIG. 3 is a block diagram of a second embodiment of the present invention;

FIG. 4 is a block diagram of a third embodiment of the invention; and,

FIGS. 5, 5A, and 5B are charts illustrating various aspects of the operation of the invention.

Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the present invention, and not for purposes of limiting same, FIG. 1 illustrates a typical intersection of two traffic lanes, i.e., lanes for which traffic signals are generated in corresponding phase A and phase B of a trafiic control system. Vehicle detectors are provided at two approaches in the intersection, to wit, detectors L-A, L-l, L-2, and L3 are located along a line to the approach for phase A, and detector L-B is located in the approach for phase B. Preferably, the other two approaches to the intersection would be provided with a corresponding arrangement of traffic detectors; however, detectors are illustrated in only two approaches to of traffic simplify the description. Detectors L-A, L-l, L-2, L-3, and L-B may take the form of loop detectors, which are well known in the art of traffic control, and generally comprise a closed wire loop embedded in a roadway, with the loop configuration defining an area under surveillance by the detector.

Vehicle detectors L-A, L-l, [1-2, L-3 and L-B are respectively connected to loop detection circuits LD-A, LD-l, LD-2, LD-3, and LD-B. These loop detector circuits may take the form of an oscillator circuit for applying a reference frequency signal to the loop detector, and when a vehicle enters the zone of influence of the loop, the inherent metallic mass of the vehicle causes a decrease in inductive reactance of the loop thereby actuating a relay coupled to the output of the oscillator circuit. Preferably, loop detector circuits LD-A, LD-l, LD-2, LD-3, and LD-B take the form of the object detection circuits disclosed in U.S. Pat. application, Ser. No. 613,257, entitled Object Detection System, filed Feb. 1, 1967, now U.S. Pat. No. 3,493,954, and assigned to the same assignee as the present invention, or other presence detectors, such as ultrasonic detectors; however, it is contemplated that various detector arrangements could be employed, including spot detectors, such as magnetic or treadle detectors. it is also contemplated that the detectors L-A and L-l through L-3 be situated with respect to each other such that an automobile located within the activated gap area, i.e., H1, H2, H3 or H4, is detected at all times by at least one of the detectors within that area. in other words, the distance between the zones of influence of adjacent detectors is less than the length of an automobile to be detected. Also, spot detectors could be substituted for the preferred presence detectors L-A, and L-l through L-3, if conventional memory circuitry were employed either external or internal of traffic controller TC in order to store signals indicated of the short-duration pulses developed by the spot detectors. With reference to FIG. 2, it is also contemplated that presence detector L-B could be replaced with a spot detector if a memory circuit is included to cause transistor 24 to remain reverse biased, once reverse biased by detector L-B and detection circuitry LD-B, until reset by other circuitry, whenever a right-of-way display is returned to phase A.

The detection circuit may generally be represented by an oscillator-amplifier circuit having its output connected through the coil of a normally open relay 12. Relay 12 of loop detection circuit LD-B includes a pair of normally open contacts l4 and 16 which are connected between the input ter minal 18 of a ramp generator RG, and ground. Also connected to input terminal 18 of ramp generator RG is the phase B detector terminal 20 of a two-phase, full-actuated traffic controller TC. Preferably, the traffic controller TC includes a maximum timer in the phase A detection circuitry for transferring the right-of-way display from phase A to phase B at a predetermined period of time after traffic has been detected in phase B, irrespective of traffic detections in phase A. It is contemplated, however, that a timing circuit could be coupled to loop detection circuit LD-A to deactivate this circuit in order to provide this maximum time function, as discussed hereinafter. As may be apparent, a plurality of detectors and associate circuitry, as illustrated in phase A, could be employed in phase B if similar traffic control is desired for phase B. in the preferred embodiment, traffic controller TC also includes a maximum timer in the phase B detection circuitry in order to return the right-of-way display to phase A at a predetermined maximum period of time after traffic has been detected in phase A, irrespective of traffic detection in phase B input terminal 18 of ramp generator RG is connected through a resistor 22 to the base of a NPN transistor 24, having its collector connected through a resistor 26 to a 8+ voltage supply source. The collector of transistor 24 is also connected through a capacitor 28 to ground, and the emitter of this transistor is connected directly to ground. Also, the collector of transistor 24 provides the output terminal 30 of ramp generator RG which is connected to the input terminals 32, 34 and 36, of differential amplifiers DA-3, DA-2, and DA-l, respectively.

Briefly, differential amplifiers DA-l, DA-2, and DA-3 are provided with reference voltage signals from level selectors LS-l, LS-2 and LS-3, respectively. The signals developed by differential amplifiers DA-l, DA-2, and DA-3 are applied expander gates G1, G2 and G3 respectively. in addition, the output signals of gates G1, G2 and G3 are applied through the normally open relay contacts of loop detection circuits LD-l, LD-2 and LD-3, respectively, to the phase A detector terminal 38 of traffic controller TC.

Preferably, differential amplifiers DA-l, DA-2 and DA3 are similar in design and operation, therefore, only differential amplifier ==,DA3 will be described in detail. input terminal 32 of differeittial amplifier DA-3 is connected to the base of an NPN transistor 40 having its emitter connected in common with the emitter of NPN transistor 42 through a resistor 43 to ground. The collectors of transistors 40 and 42 are respectively connected through a pair of resistors 44 and 46 to the 13+ voltage supply source, and the collector of transistor 40-also provides an output terminal 48 of differential amplifier DA-3. The base of transistor 42 is connected to the movable arm of a potentiometer 50 in level-selector circuit LD-3. Level-selector circuits LD-l, LS-2 and LS-3 preferably take the same form and are generally comprised of potentiometer 50 having one of the stationary contacts connected to the B+ voltage supply source, and the other stationary contact of potentiometer 50 is connected directly to ground. 7

The output terminal 48 of differential amplifier DA-3 is connected to an input terminal 52 of expander gate G3. Expander gate G3 takes the same form as gates G1 and G2, and generally comprises a resistor 54 connected between the input terminal 52 and the base of an NPN transistor 56, having its emitter connected directly to ground. The collector of transistor 56 provides the output terminal 58 of gate G3 which is coupled to loop detection circuit LD-3.

Loop detection circuits LD-A, LD-l, LD-2, and LD-3, preferably take the same form as loop detection circuit LD-B; therefore, similar elements are designated with like reference numerals. Normally open relay contacts 14 and 16 of relay 12 in loop detection circuit LD-3 are connected in series between an output terminal 58 of gate G3 and phase A detector terminal 38. Loop detection circuit LD-A is connected into the circuit similar to detector LD-3; however, relay contact 14 of detector circuit LD-A is connected directly to ground.

OPERATION Having now described the circuit arrangement of the preferred embodiment, reference is now made to FIGS. 1, 2, and 5, which graphically illustrated a preferred procedure of practicing a method, in accordance with the invention, for controlling traffic flow through the intersection illustrated in FIG. 1.

Assuming the initial condition is that a vehicle in lane A has the right-of-way, when a vehicle in lane B is detected, the loop detector circuit LDB applies a ground potential signal through contacts l4, 16 of relay 12 to full-actuated traffic controller TC. in the event no vehicles are located in phase A, a change in right-of-way will occur as soon as a yellow signal is displayed for phase A. If, however, vehicles are located in the lane of phase A, then the right-ofway will transfer as soon as none of the detectors L-A through L-3 are detecting a vehicle.

In addition to actuating the full-actuated tratfic controller TC, the output signal developed by loop detector circuit LD-B applies a reverse bias signal to transistor 24 of ramp generator RG. With transistor 24 in a reverse-biased condition, capacitor 28 commences charging thereby causing an increasing voltage signal to be generated at output terminal 30 of ramp generator RG. This increasing voltage signal is applied to differential amplifiers DA-l, DA-Z, and DA-3. As this voltage becomes greater than the level set by level selectors LS-l, LS-2, and LS-3, loop detector circuits LD-3, and LD-2, and LD1 become deactivated, leaving only loop detector LD-A in operation.

With reference to FIG. 2, when loop detector circuit LD-B detects a vehicle, the output signal is amplified by amplifier and is applied to the coil of normally open relay 12 thereby energizing this relay. Upon activation of relay 12, the normally open contacts l4, 16 of relay 12 close, thereby applying a ground potential signal to phase B of tratfic controller TC, as well as to the base of transistor 24 in ramp generator RG. This ground potential signal reverse biases transistor 24 and capacitor 28 commences to charge toward the value of the potential of the B.+ supply source. This increasing potential, as shown by waveform V in FIG. 5, is applied to differential amplifiers DA-l, DA-2, and DA-3. The first loop detector circuit to be effected by this increasing voltage signal is loop detector circuit LD-3. Transistor 40 in difi'erential amplifier DA-3 is normally reverse biased and transistor 42 is normally forward biased by the adjustment of potentiometer 50 in the level selector LS-3. When the positive-going voltage V increases to a value slightly greater than the output voltage applied to transistor 40, transistor 40 becomes biased into conduction to thereby apply a ground potential signal to the base of transistor 56 in expander gate G3. Thus, transistor 56, which is normally forward biased, becomes reverse biased to thereby prevent contact 16 of relay 12 in loop detector circuit LD-3 from being connected to ground when a vehicle is located in the zone of influence of loop L-3. Thus, loop L-3, and its loop detector circuit LD-3 become deactivated or deenergized. The point at which loop detector circuit LD-3 becomes deenergized is shown as time t, in FIG. 5, where voltage V equals the value of the voltage signal applied to differential amplifier DA3 by ramp generator RG. Time t, represents the time at which loop detector LD-B is activated by a vehicle located in the zone of influence of loop L-B. In a similar manner, loop detector circuit LD-2 becomes deactivated at a time t, as shown in FIG. 5. Thereafter, loop detector circuit LD-l becomes deactivated, as shown by time 1 in FIG. 3. At this point, the operation of traffic controller TC is somewhat similar to that of conventional, full-actuated traffic controllers. Thus, after a vehicle located within the zone of influence of loop L-A passes out of this zone of influence, then the controller will commence to display a caution signal to vehicles in lane A, and thereafter allocate right-of-way to vehicles in lane B.

When the traffic being detected by the vehicle detection means L-B moves through the intersection, normally open relay contact 14 again opens to thereby cause transistor 24 to again become forward biased. As transistor 24 becomes forward biased, capacitor 28 again discharges from the collector to the emitter of transistor 28 thereby resetting loop detection circuits LD-A through LD-3. In other words, when traffic is detected by loop detector I..-B, a signal is applied to loop detection circuit LD-B, which in turn, develops a signal which is applied to phase B detector terminal of traffic controller TC. The signal developed by loop detection circuit LD-B is also applied to generator RG. When this signal is applied to ramp generator RG, this circuit commences generating a signal which increases in value with respect to time. This signal generated by ramp generator RG is applied to differential amplifier DA-l so that when the applied signal attains a predetermined value, differential amplifier DA-l is actuated from a first condition to a second condition to thereby deactivate loop detection circuit LD-l. Similarly, when the signal developed by ramp generator RG attains a second and third predetermined level, differential amplifiers are actuated to deactivate loop detection circuits LD-2 and LD-3.

Also, it is contemplated that loop detector circuit LD-A may, in a manner similar to detector circuits LD-l through LD-3, be connected to a differential amplifier and a levelselector circuit, as well as ramp generator RG, and this circuit arrangement would serve as a maximum timeout circuit for lane A, if such is desired.

Briefly, the method in accordance with the invention for controlling the operation of a traffic signal means TC for allocating go" and stop signals to vehicles in at least a first and second traffic lane utilizes vehicle detection means L-B associated with the first traffic phase for detecting vehicles in the first traffic lane; first and second detection means L-l, L-A, associated with the second phase for detecting vehicles in the second traffic lane; first circuit means LD-B coupled to the vehicle detection means L-B for developing a signal in response to the detection of traffic by the vehicle detection means L-B; second and third circuit means LD-l, LD-A coupled to the first and second detection means L-l, L-A. The steps in accordance with the method include: energizing the traffic signal means S, under control of traffic controller TC, to display a stop signal to vehicles in one of said trafiic lanes and a go signal to vehicles in the other one of said trafi'rc lanes; activating the first, second and third circuit means LDB, LD-l, LD-A; detecting traffic in one of the traffic lanes with the vehicle detection means L-B; developing a signal with the first circuit means LD-B in response to a detection of traffic by the vehicle detection means L-B; detecting traffic in the other of the traffic lanes with the first and second detection means L-l, L-A; developing a control signal with the second and third circuit means LD-l, LD-A in response to the detection of a vehicle by the first or said second detection means L-l, L-A, respectively; applying a control signal developed by the second and third circuit means LD-l, LD-A to a trafiic signal means to thereby allocate the go and stop signals to the traffic lanes; deactivating the second circuit means LD-l at a predetermined period of time afier a signal is developed by the first circuit means LD-B so that at a said predetermined period of time after a signal is developed by the first circuit means LD-B the first detection means L-l becomes ineffective in controlling the operation of a traffic signal means in allocating go and stop signals to the traffic lanes.

Preferably the signal developed by ramp generator takes the form of a voltage signal which increases in value exponentially with respect to time; however, it is contemplated that a ramp generator having an output signal which increases linearly with respect to time could be employed, as will be discussed hereinafter.

In the preferred embodiment, loops L-A, L-l, L-2, and L-3 are linearly spaced along a line which is generally parallel to the axis of lane A; however, various spacing configurations are contemplated within the scope of this invention. Thus, with linear spacing between the detector loops, the total gap distance within the zone of influence of the energized loops decreases linearly from gap H1 to gap H4 with the passage of time, assuming the voltage developed across capacitor 28 increases linearly with time. If, however, the detector loops are exponentially spaced, the total zone of influence will decrease exponentially from gap R1 to gap PM with respect to time assuming the voltage developed across capacitor 28 increases linearly with time. More particularly, with reference to FIGS. 5 and 5A, it is readily apparent that with linear spacing between the loops, the total gap decreases exponentially with respect to time, assuming the voltage developed across capacitor 28 increases exponentially with time. With exponentially spaced loops, the total average gap area decreases approximately linearly with respect to time, as illustrated in FIG. 5B. In other words, with detector loops L-A, L- l, L-Z, and L-3 spaced exponentially, the total average gap area will decrease linearly even though the voltage developes across capacitor 28 increases exponentially with time. Various detector loop configurations, spacing, and number of detectors, such as N detectors, could be employed to meet a particular traffic demand of the intersection.

In the preferred embodiment the spacing between adjacent loops is less than the length of a vehicle to be detected, such as 6 feet, so that the energized loop detection circuits are continuously activated by the vehicle; however, it is contemplated that this spacing could exceed'the length of a vehicle to be detected if the traffic controller TC included a memory circuit in the lane A detector circuitry to retain the detection information. Alternately, memory circuitry could be included within each loop detection circuit. Preferably, each of the detector loops is of substantially the same dimension; however, various loop sizes and configurations are within the scope of this invention. For example, if detector loop L-A provides a larger zone of influence than loops L-l, L-2, and L-3, the traffic control system would continue to operate as a conventional, two-phase actuated traffic controller in the event loop detection circuits LD-l, LD-2, and LD-3 fail to operate.

GAP REDUCTION CIRCUIT HAVING A COMMON DETECTOR CIRCUIT Reference is now made to FIG. 3 which illustrates a second embodiment of the present invention, and is generally comprised of detector loops L-A, L-I, and L-2 for the approaches of lane A, and detector loop L-B for lane B, of a two-phase traffic intersection. Detector loops L-A, L-l, L-2, and L-B preferably take the same form as the loop detectors illustrated in FIG. 1. Detector loops L-A, L-l, and L-2 are respectively connected to a plurality of bridge and amplifier circuits BA-A, BA-I, and BA-Z, which are in turn, connected to a scanner circuit S. Also, detector circuit L-B is connected to a loop detection circuit LD-B, which is in turn, connected to scanner circuit S and the phase B detector terminal 60 of a two phase, full-actuated traffic controller TC. Scanner circuit S is connected through a threshold detector and relay circuit TD to the phase A detector terminal 62 of traffic controller TC. In addition, traffic controller TC is connected to the reset terminal of scanner circuit S.

Loop detection circuit LD-B is similar to the corresponding circuit illustrated in FIG. 1, and bridge and amplifier circuits BA-A, BA-l, and BA-2 are preferably similar to loop detec tion circuit LD-B illustrated in FIG. I. In the preferred embodiment, scanner circuit S is comprised of a shift register, such as the shift register illustrated on page 134, FIG. 5.10, of the General Electric Transistor Manual, Seventh Edition, 1964. More particularly, the shift register circuit is actuated when a vehicle is detected by loop detection circuit LD-B, and provides an output function somewhat similar to that of differential amplifier DA-3, and expander gate G3 of the embodiment shown in FIG. 1. Thus, scanner circuit S prevents the signal of the deactivated bridge and amplifier circuit from being applied to the threshold detector and relay circuit TD.

As the shift register in scanner circuit S commences a counting or scanning operation, upon being triggered by the signal developed by loop detection circuit LD-B, the shift register sequentially interrupts the circuit connections between bridge and amplifier circuits BA-A, BA-l, and BA-2, and the threshold detector and relay TD. Threshold detector and relay circuit D are generally comprised of an amplifier circuit for receiving the signal developed by scanner S and activating a relay, to thereby couple phase A detector terminal 62 of traffic controller TC to a ground potential, in response to the signal developed by scanner circuit S. Scanner circuit S is reset simultaneously with the display of a stop signal to phase A of traffic controller TC.

GAP REDUCTION CIRCUIT HAVING A COMMON LOOP CONFIGURATION Reference is now made to FIG. 4 which illustrates a third embodiment of the present invention, and is generally comprised of a plurality of detector loops L-A, L-l, L-2, and L-3 each having a common loop side, and being connected to a scanner circuit S. Also, a detector loop LD-B for detecting vehicles in lane B is connected through a loop detection circuit LD-B, to scanner circuit S and lane B detector terminal 70 of trafl'rc controller TC. The common side of detector loops IrA, L-l, L-2, and L-3 is connected directly to bridge and amplifier circuit BA-C, which is in turn connected through a presence tuning circuit P and threshold detector circuit TD to phase A detector terminal 72 of traffic controller TC. In addition, loop tuning circuit L is coupled between scanner circuit S, and bridge amplifier circuit BA-C. Scanner circuit S, bridge and amplifier circuit BA-C, and threshold detector TD, are preferably similar in design and operation to the corresponding circuits illustrated in FIG. 3.

Loop tuning circuit L, and presence tuning circuit P, are preferably of the type disclosed in U.S. Pat. application, Ser. No. 613,257, now U.S. Pat. No. 3,493,954 entitled Object Detection System, filed Feb. I, 1967, and assigned to the same assignee as the present invention. The operation of the gap reduction circuit illustrated in FIG. 4 is similar to the operation of the circuit illustrated in FIG. 3; however, since the size of the detector loop connected to bridge and amplifier circuit BA-C varies from the relatively small-size loop L-A to the large-size loop L-3, it is necessary that a loop tuning circuit L be provided to rebalance the bridge circuit of bridge and amplifier circuit BA-C, each time the size of the detector loop changes. For example, if the bridge circuit of bridge and amplifier circuit BA-C is tuned to the inductance exhibited by loop L-A, when loop L-l is connected to bridge and amplifier circuit BA-C, the bridge circuit must be rebalanced to compensate for the additional inductance exhibited by loop L-l.

Presence tuning circuit P, being somewhat similar to the presence tuning circuit disclosed in the above-mentioned patent application, provides a tuning circuit which is coupled to the bridge circuit of bridge and amplifier circuit BA-C to thereby rebalance the bridge circuit, so as to tune out a vehicle which may be stalled in the detection zone, and thereafter continue to be responsive to the presence of additional vehicles in the detection zone.

Thus, with the circuit configuration as illustrated in FIG. 4, gap reduction may be accomplished with a plurality of detector loops each having a common side. In addition, with this circuit configuration, a single bridge and amplifier circuit BA-C, presence tuning circuit P, and threshold detector cir cuit TD, may be employed to provide a signal in response to a vehicle detection by a plurality of detector loops.

The invention has been described in connection with a particular preferred embodiment, and two variations thereof, but is not to be limited to these embodiments. Various modifications may be made without departing from the scope and spirit of the present invention as defined by the appended claims.

Having thus described our invention, we claim:

1. In a trafiic control system for alternately allocating go and stop signals to at least a first and second conflicting traffic lane, said first traffic lane having vehicle detection means associated therewith for detecting vehicles in said first traffic lane; said second traffic lane having at least a first and second detections means associated therewith for, when activated, detecting vehicles in said second traffic lane; the combination with said vehicle detection means comprising:

first circuit means coupled to said vehicle detection means for developing a signal upon detection of a vehicle by said vehicle detection means;

means for activating said first and second detection means;

second circuit means coupled to said first and second detection means for developing a control signal upon detection of a vehicle by either of said first or second detection means; and,

timing circuit means coupled to said first detection means for deactivating said first detection means at the end of a predetermined period of time after a said signal is developed by said first circuit means.

2. The combination set forth in claim 1 wherein said first and second detection means are generally situated along a line extending substantially parallel to the axis of said second traffic lane.

3. The combination set forth in claim 1 including circuit means for maintaining said second detection means in an activated condition for a said predetermined period of time after a signal is provided by said first circuit means.

4. The combination set forth in claim 3 wherein the space between said first and said second detection means is less than 12 feet so that when said first and second detection means are activated, a continuous control signal is developed by said second circuit means upon passage of traffic from said first to said second detection means.

5. The combination set forth in claim 3 including a third detection means associated with said second traffic lane for detecting vehicles in said second lane.

6. The combination set forth in claim 5 wherein said first, second, and third detection means are spaced substantially linearly with respect to each other so that a zone of influence defined by the activated detection means reduces linearly upon deactivation of said second and third detection means respectively.

7. The combination set forth in claim 5 wherein said first, second, and third detection means are spaced substantially with respect to each other so that a zone of influence defined by the activated detection means reduces exponentially upon deactivation of said second and third detection means respectively.

8. The combination set forth in claim 5 wherein said first, second, and third detection means are generally located along a line extending substantially parallel with the axis of said second traffic lane.

9. The combination set forth in claim 5 including circuit means coupled to said third detection means for deactivating said third detection means at a third predetermined period of time after a said signal is provided by said first circuit means upon actuation of said vehicle detection means of said first traffic lane.

10. The combination set forth in claim 1 wherein said timing circuit means is coupled to said first and said second detection means for deenergizing said first and said second detection means at a first and second predetermined period of time, respectively, after a said signal is provided by said first circuit means.

11. The combination set forth in claim 1 wherein said timing circuit means includes generator circuit means for, upon receipt of a said signal from said first circuit means, developing a timing signal which increases in value with respect to time; and comparator circuit means having a first and second condition and an output circuit means for deactivating said first detection means when said comparator circuit means is actuated to said second condition; said comparator circuit means for monitoring said timing signal developed by said generator circuit means so that when timing signal attains a predetermined level said comparator circuit means is actuated from said first condition to said second condition to thereby cause said first detection means to become deactivated.

12. The combination set forth in claim 11 wherein said output circuit means of said comparator circuit means includes an electronic control means being normally conductive, and upon actuation of said comparator circuit means from said first condition to said second condition, said electronic control means becomes nonconductive to thereby deactivate said first detection means.

13. The combination set forth in claim 1 wherein said means for activating said first and second detection means includes scanner circuit means for selectively activating said first and said second detection means.

14. The combination set forth in claim 2 wherein said first detection means includes a sensing means for detecting the presence of traffic situated within a first predetermined area within said second traffic lane; and said second detection means includes a sensing means for detecting the presence of traffic situated situated a second predetermined area being larger than said first predetermined area.

15. A method of controlling the operation of a traffic signal means for allocating go and stop signals to at least a first and second conflicting trafiic lane by utilizing vehicle detection means associated with said first trafiic lane, first and second detection means associated with said second traffic lane, first circuit means coupled to said vehicle detection means and comprising the steps of:

a. activating said traffic signal means to display a stop signal in one of said traffic lanes and a go signal in the other one of said traffic lanes;

b. activating said first, second and vehicle detection means;

c. detecting traffic in one of said traffic lanes with said vehi cle detection means;

d. developing a signal with said first circuit means in response to a said detection of traffic by said vehicle detection means;

e. detecting traflic in the other of said traffic lanes with said first and second detection means;

f. developing control signals with said first and second detection means in response to the detection of a vehicle by said first and said second detection means, respectively;

g. applying said control signals developed by said first and said second detection means to a said traffic signal means to thereby allocate said go and stop signals to said traffic lanes;

h. deactivating said first detection means at a predetermined period of time after a said signal is developed by said first circuit means so that at a said predetermined period of time after a signal is developed by said first circuit means the first detection means becomes ineffective in controlling the operation of a said traffic signal means in allocating go and stop signals to said traffic lanes.

16. A method of controlling the operation of a traffic signal means as set forth in claim 15 including the additional step of deactivating said second detection means at a second predetermined period of time after a signal is developed by said first circuit means so that at said second predetermined period of time after a signal is developed by said first circuit means, the second detection means becomes ineffective in controlling the operation of a said traffic signal means in allocating go and stop signals to said traffic lanes.

17. A method of controlling the operation of a traffic signal means as set forth in claim 15 including the additional step of reactivating said first detection means.

18. A method of controlling the operation of a traffic signal means as set forth in claim 16 including the additional step of reactivating said first and said second detection means.

19. A method of controlling the operation of a traflic signal means for allocating go and stop signals to at least a first and second conflicting traffic lane by utilizing vehicle detection means associated with said first traffic lane, N detection means associated with said second traflic lane, first circuit means coupled to said vehicle detection means, and N circuit means each respectively coupled to one of said N detection means and comprising the steps of:

a. activating said traffic signal means to display a stop signal to one of said trafiic lanes and a go signal to the other one of said traffic lanes;

b. activating said vehicle detection means and said N detection means;

c. detecting traffic in one of said trafiic lanes with said vehicle detection means;

d. developing a signal with said first circuit means in response to a said detection of traffic by said vehicle detection means;

e. detecting traffic in the other of said trafiic lanes with said N detection means;

f. developing control signals with said N circuit means in response to the detection of a vehicle by any of said N detection means;

g. applying said control signals developed by said N circuit means to a said traffic signal means to thereby allocate said go and stop signals to said traffic lanes; and,

h. deactivating one of said N detection means at a predetermined period of time after a said signal is developed by said first circuit means.

20. A method of controlling the operation of a traffic signal means as set forth in claim 19 including the additional steps of sequentially deactivating the others of said N circuit means.

21. A method of controlling the operation of a traffic signal means as set forth in claim 19 including the additional steps of sequentially deactivating N-l of the others of said N circuit means.

22. A method of controlling the operation of a traffic signal means for allocating go and stop signals to at least a first and second conflicting traffic lane by utilizing at least first and second detection means associated with one of said traffic lanes and means for allocating a go signal periodically to vehicles in a second lane intersecting said one lane and comprising the steps of:

a. positioning said first and second detection means generally along a line parallel to the axis of said one traffic lane;

b. activating said first and second detection means;

c. developing periodic control signals for activating a go signal in said second lane;

d. developing control signals with said first and second detection means in response to the detection of a vehicle by said first and second detection means;

e. applying said control signals to said traffic control means to thereby allocate said go and stop signals to said traffic lanes;

f. deactivating said first detection means at a predetermined time after each development of said first-mentioned control signals so that said first detection means is inefi'ective in controlling the operation of a said traffic signal means in allocating go and stop signals to said trafiic lanes. 

1. In a traffic control system for alternately allocating go and stop signals to at least a first and second conflicting traffic lane, said first traffic lane having vehicle detection means associated therewith for detecting vehicles in said first traffic lane; said second traffic lane having at least a first and second detections means associated therewith for, when activated, detecting vehicles in said second traffic lane; the combination with said vehicle detection means comprising: first circuit means coupled to said vehicle detection means for developing a signal upon detection of a vehicle by said vehicle detection means; means for activating said first and second detection means; second circuit means coupled to said first and second detection means for developing a control signal upon detection of a vehicle by either of said first or second detection means; and, timing circuit means coupled to said first detection means for deactivating said first detection means at the end of a predetermined period of time after a said signal is developed by said first circuit means.
 2. The combination set forth in claim 1 wherein said first and second detection means are generally situated along a line extending substantially parallel to the axis of said second traffic lane.
 3. The combination set forth in claim 1 including circuit means for maintaining said second detection means in an activated condition for a said predetermined period of time after a signal is provided by said first circuit means.
 4. The combination set forth in claim 3 wherein the space between said first and said second detection means is less than 12 feet so that when said first and second detection means are activated, a continuous control signal is developed by said second circuit means upon passage of traffic from said first to said second detection means.
 5. The combination set forth in claim 3 including a third detection means associated with said second traffic lane for detecting vehicles in said second lane.
 6. The combination set forth in claim 5 wherein said first, second, and third detection means are spaced substantially linearly with respect to each other so that a zone of influence defined by the activated detection means reduces linearly upon deactivation of said second and third detection means respectively.
 7. The combination set forth in claim 5 wherein said first, second, and third detection means are spaced substantially with respect to each other so that a zone of influence defined by the activated detection means reduces exponentially upon deactivation of said second and third detection means respectively.
 8. The combination set forth in claim 5 wherein said first, second, and third detection means are generally located along a line extending substantially parallel with the axis of said second traffic lane.
 9. The combination set forth in claim 5 including circuit means coupled to said third detection means for deactivating said third detection means at a third predetermined period of time after a said signal is provided by said first circuit means upon actuation of said vehicle detection means of said first traffic lane.
 10. The combination set forth in claim 1 wherein said timing circuit means is coupled to said first and said second detection means for deenergizing said first and said second detection means at a first and second predetermined period of time, respectively, after a said signal is provided by said first circuit means.
 11. The combination set forth in claim 1 wherein said timing circuit means includes generator circuit means for, upon receipt of a said signal from said first circuit means, developing a timing signal which increases in value with respect to time; and comparator circuit means having a first and second condition and an output circuit means for deactivating said first detection means when said comparator circuit means is actuated to said second condition; said comparator circuit means for monitoring said timing signal developed by said generator circuit means so that when timing signal attains a predetermined level said comparator circuit means is actuated from said first condition to said second condition to thereby cause said first detection means to become deactivated.
 12. The combination set forth in claim 11 wherein said output circuit means of said comparator circuit means includes an electronic control means being normally conductive, and upon actuation of said comparator circuit means from said first condition to said second condition, said electronic control means becomes nonconductive to thereby deactivate said first deTection means.
 13. The combination set forth in claim 1 wherein said means for activating said first and second detection means includes scanner circuit means for selectively activating said first and said second detection means.
 14. The combination set forth in claim 2 wherein said first detection means includes a sensing means for detecting the presence of traffic situated within a first predetermined area within said second traffic lane; and said second detection means includes a sensing means for detecting the presence of traffic situated situated a second predetermined area being larger than said first predetermined area.
 15. A method of controlling the operation of a traffic signal means for allocating go and stop signals to at least a first and second conflicting traffic lane by utilizing vehicle detection means associated with said first traffic lane, first and second detection means associated with said second traffic lane, first circuit means coupled to said vehicle detection means and comprising the steps of: a. activating said traffic signal means to display a stop signal in one of said traffic lanes and a go signal in the other one of said traffic lanes; b. activating said first, second and vehicle detection means; c. detecting traffic in one of said traffic lanes with said vehicle detection means; d. developing a signal with said first circuit means in response to a said detection of traffic by said vehicle detection means; e. detecting traffic in the other of said traffic lanes with said first and second detection means; f. developing control signals with said first and second detection means in response to the detection of a vehicle by said first and said second detection means, respectively; g. applying said control signals developed by said first and said second detection means to a said traffic signal means to thereby allocate said go and stop signals to said traffic lanes; h. deactivating said first detection means at a predetermined period of time after a said signal is developed by said first circuit means so that at a said predetermined period of time after a signal is developed by said first circuit means the first detection means becomes ineffective in controlling the operation of a said traffic signal means in allocating go and stop signals to said traffic lanes.
 16. A method of controlling the operation of a traffic signal means as set forth in claim 15 including the additional step of deactivating said second detection means at a second predetermined period of time after a signal is developed by said first circuit means so that at said second predetermined period of time after a signal is developed by said first circuit means, the second detection means becomes ineffective in controlling the operation of a said traffic signal means in allocating go and stop signals to said traffic lanes.
 17. A method of controlling the operation of a traffic signal means as set forth in claim 15 including the additional step of reactivating said first detection means.
 18. A method of controlling the operation of a traffic signal means as set forth in claim 16 including the additional step of reactivating said first and said second detection means.
 19. A method of controlling the operation of a traffic signal means for allocating go and stop signals to at least a first and second conflicting traffic lane by utilizing vehicle detection means associated with said first traffic lane, N detection means associated with said second traffic lane, first circuit means coupled to said vehicle detection means, and N circuit means each respectively coupled to one of said N detection means and comprising the steps of: a. activating said traffic signal means to display a stop signal to one of said traffic lanes and a go signal to the other one of said traffic lanes; b. activating said vehicle detection means and said N detection means; c. detecting traffic in one of said traffic lanes with said vEhicle detection means; d. developing a signal with said first circuit means in response to a said detection of traffic by said vehicle detection means; e. detecting traffic in the other of said traffic lanes with said N detection means; f. developing control signals with said N circuit means in response to the detection of a vehicle by any of said N detection means; g. applying said control signals developed by said N circuit means to a said traffic signal means to thereby allocate said go and stop signals to said traffic lanes; and, h. deactivating one of said N detection means at a predetermined period of time after a said signal is developed by said first circuit means.
 20. A method of controlling the operation of a traffic signal means as set forth in claim 19 including the additional steps of sequentially deactivating the others of said N circuit means.
 21. A method of controlling the operation of a traffic signal means as set forth in claim 19 including the additional steps of sequentially deactivating N-1 of the others of said N circuit means.
 22. A method of controlling the operation of a traffic signal means for allocating go and stop signals to at least a first and second conflicting traffic lane by utilizing at least first and second detection means associated with one of said traffic lanes and means for allocating a go signal periodically to vehicles in a second lane intersecting said one lane and comprising the steps of: a. positioning said first and second detection means generally along a line parallel to the axis of said one traffic lane; b. activating said first and second detection means; c. developing periodic control signals for activating a go signal in said second lane; d. developing control signals with said first and second detection means in response to the detection of a vehicle by said first and second detection means; e. applying said control signals to said traffic control means to thereby allocate said go and stop signals to said traffic lanes; f. deactivating said first detection means at a predetermined time after each development of said first-mentioned control signals so that said first detection means is ineffective in controlling the operation of a said traffic signal means in allocating go and stop signals to said traffic lanes. 